Presentation

Rapid Thermally Enhanced
Degradation of Methylene Chloride at
a Spill Site in the UK
Jay Dablow, James Baldock
RemTech 2015
October 14-16, 2015
Fairmont Banff Springs
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Background
■ Methylene Chloride (Dichloromethane) was accidentally
released from an underground pipe, directly into
groundwater (approximately 15,000kg)
■ Unusual Project
■ Recent spill, not a planned legacy project
■ Emergency response
■ Speed - time of the essence: carried out design/installation in
parallel
■ Third party land impacted/remediated
■ Site fully operational and treatment zone in high activity area
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Sustainability throughout Project Lifecycle
ERM has integrated the SuRF framework with key stages in project delivery
Stage B - Setting the remediation
technical approach
Stage A - Setting the remediation
specification and strategy
CLIENT
OBJECTIVE
PROJECT
DEFINITION
PLANNING
(brownfield)
SITE
INVESTIGATION
RISK
ASSESSMENT
REMEDIAL
OPTIONS
APPRAISAL
REMEDIATION
CONSTRUCTION
REMEDIATION
OPTIMISATION
CLIENT
GOAL
Community & stakeholder engagement
Sustainable Procurement
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Site Characterization
DNAPL observed during investigation
GW Flow
Spill
■ HRSC has lower carbon
footprint than traditional SI
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Remedial Options Appraisal: MCA Results
■ Steam enhanced vacuum extraction
selected on the basis of:
■ Challenge of water management
■ Large mass spilt into ground (11,000 litres)
■ Rapid remediation required
■ Relatively stringent remedial goals
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■ Low boiling point of DCM
Sustainable Remedial Design
■ Electrical boiler converted to run on gas (increased energy efficiency)
■ Process equipment to reduce GAC use
■ Optimize steam heating – via a thermal model
■ Operational approach included heat re-use (up-gradient injection first)
■ Thermal processes. Originally expected volatilization would be key
mechanism (DCM BP 40°C, but evaluated abiotic or biotic processes)
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System Installation: Steam Boiler
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System Installation: Vapour/Liquid Processing
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System Installation: Carbon Treatment
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System Installation: Pipework
Vapor extraction well head
Steam injection well head
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Groundwater Sampling – DCM Results (Baseline)
Jan/Feb 2014
(Baseline)
10m
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Some migration since
HRSC, but majority of
mass remained onsite
Remedial Strategy
TMP – 1.7, 3.0,5.0 varies
1m
Steam Injection Well
Extraction Well
5m
Thermocouple String
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System Operation: Thermocouple Data Example
Top
Intermediate
Base
°C
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Heating optimization – track
temperatures, reduce energy
consumption
Expected Mass Recovery Mechanisms (2)
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Actual Mass Recovery (August 2014)
500
450
400
Mass recovered (kg)
350
300
250
200
150
100
50
0
Date
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Vapour Phase Recovery
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Hydrous Pyrolysis Oxidation
Liquid Phase Recovery
Groundwater Sampling – DCM Results (August 2014)
August 2014
Jan/Feb 2014 (Baseline)
Data indicates >90%
DCM reduction
achieved (16 weeks
operational time)
10m
10m
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Chloride Distribution (August 2014)
Jan/Feb 2014 (Baseline)
Zone of limited
heating
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Cl conc.
DCM Degradation Mechanisms
■ Reaction Chemistry:
■ Aerobic thermophillic biodegradation:
■ CH2Cl2 + O2  CO2 + 2HCl
■ Thermal hydrolysis:
■ CH2Cl2 + 2OH-  HCHO + 2Cl- + H2O
■ Biological degradation initially suspected:
■ Large sulfate reduction pre-thermal
■ Significant CO2 removal during heating
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DCM Degradation Mechanisms (2)
■ But post thermal microbial population decreased
■ Chloride may also be derived from abiotic
mechanisms (hydrolysis) and a single round of
CSIA confirmed abiotic degradation has occurred –
but only one sample event
■ Ultimately, hard to resolve exact mechanism, but
significant reductions observed and remainder of
treatment zone heated to lower temperatures to
complete the project
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DCM Concentration Results (October 2014)
Jan/Feb 2014 (Baseline)
■ >95% DCM
reduction
achieved
■ Low temperature
mechanisms
enabled 5 week
project duration
reduction
■ Regulatory
approval
obtained. No
further action
required and
prosecution
avoided
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October 2014
Conclusions
■ Despite energy consumption, thermal techniques directed
at source reduction offer a lower carbon footprint,
especially when sustainable design and operational
approaches are applied
■ Carbon Footprint Reduction
■ Accurate source zone delineation
■ Multi-Criteria Analysis
■ Gas powered heating process
■ Process engineering innovation
■ Optimized heat control and delivery
■ Low temperature mechanisms observed
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Questions?
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